KR20190100925A - How to recover heat from hydrocarbon separation - Google Patents

Abstract

Systems and methods for heat recovery associated with separation of hydrocarbon components. Two compressors are used to compress a portion of the overhead vapor stream from the fractionation column. The pressure of the liquid portion of the compression overhead is reduced and used to recover heat from the overhead of another separation zone with a fractionation column. Once the heat is recovered, the stream is recompressed. The recovered heat can be removed from the recompression stream in the reboiler of another fractionation column. The fractionation column may include a deethanizer splitter, a propane-propylene splitter, and a depropanizer column.

Description

How to recover heat from hydrocarbon separation

Priority statement

This application claims priority to US Application No. 62/440111, filed December 29, 2016, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present invention generally relates to processes and systems associated with recovering heat from hydrocarbon separation processes.

Petroleum refining and petrochemical processes often involve separating hydrocarbon components having very similar structures and properties.

For example, propylene-propane splitters are typically used to separate a hydrocarbon stream into a polymer grade propylene (PGP) stream as a net overhead stream and a stream with propane in the net bottoms. It includes a distillation column. Due to the low relative volatility of propylene and propane, very large towers with typically 150 to 250 trays are used. In addition, the tower also typically requires a reflux to feed ratio of 5 to 10 to effect separation. Since the relative volatilities of propylene and propane are too low (typically 1.05 to 1.20), fractionation is energy intensive to separate propylene and propane into a high purity component stream.

Typically, condensation at the fractionation column overhead is similar because the vapor pressures of propylene and propane are similar and the heat removed from the column overhead for condensation can be transferred or pumped to the bottom of the tower for re-boiling. Heat pump compressors are used to remove (or remove energy) and to reboile (or to supply energy) down the column.

In some designs, such as those disclosed in US Patent Application Publication No. 2013/0131417, assigned to the assignee of the present invention and incorporated herein by reference in its entirety, overhead vapor from a propylene-propane splitter column ("PP splitter") The first stage is sent to a heat pump compressor. The stream separated in the PP splitter is typically from an upstream deethanizer. In a first stage heat pump compressor, the overhead steam of the PP splitter is compressed to the required pressure, typically between 150 and 250 psig, typically 1,034 to 1,724 ng (g), the heat exchanger condensing the steam on the hot side of the heat exchanger and The minimum temperature for reboiling the liquid at the low temperature side of. The duty required to reboile the PP splitter determines the steam flow rate to the reboiler / condenser. Since the condensation duty is greater than the reboiling duty of the PP splitter, there is excess steam from the first stage discharge requiring condensation. This excess steam is sent to the second stage of the heat pump compressor, where it can be compressed to a pressure that can be condensed by another heat exchanger at a warmer temperature. Subsequently, this stream is flashed across the valve into the suction drum up to the column overhead pressure to provide Joule-Thomson effect cooling to the column overhead and accumulate propylene liquid product in the suction drum. . In such a system described above, when the second stage discharge stream is flashed up to the column overhead pressure, the resulting vapor from this flash is subsequently reprocessed sequentially in the heat pump first and second stages. Thus, the first stage of the heat pump compressor, which is a larger capacity stage that requires greater utility, needs to treat the column overhead steam together with the steam from the second stage discharge flash, so that the compressor's overall capacity and availability requirements To increase.

Another system for recovering heat from a PP splitter is disclosed in US Pat. No. 7,981,256, which is also assigned to the assignee of the present invention and incorporated herein by reference in its entirety. In the design shown in US Pat. No. 7,981,256, a multi-stage heat compressor system is used to transfer heat from the overhead stream of the PP splitter to the reboiler for the PP splitter. This application uses at least three steps and still requires an external refrigeration system for the upstream deethanizer.

Another design disclosed in US Patent Application Publication No. 2015/0101921, assigned to the applicant of this application and incorporated herein by reference in its entirety, utilizes a single two-stage compressor. The systems and processes disclosed in US Patent Application Publication No. 2015/0101921, incorporated herein by reference, recognize that the cooling system required to condense the deethanizer rectifier is often expensive. However, the heat removed for PP splitter overhead condensation is wasted by air or cooling water.

These designs are probably effective for their intended purpose, but there is a continuing need to develop and provide processes that improve energy efficiency and heat recovery.

Systems and processes have been found that enable more efficient heat recovery associated with the separation of hydrocarbons, using single stage heat pump compressors and multistage heat recovery compressors. This configuration condenses the deethanizer using the liquid from the heat recovery compressor second stage suction drum. Additionally, the liquid from the heat recovery second stage suction drum is pumped to the reservoir as net propylene liquid product (column net overhead product). A propylene trim cooler can be used to supercool the liquid from the depropanizer reboiler outlet flashed back to the heat recovery second stage suction drum. It is contemplated to reboile the downstream depropanizer column using additional heat contained within the stream.

In this configuration, steam from the PP splitter column overhead is processed in a single stage heat pump compressor. The heat pump compressor is preferably a centrifugal compressor with anti-surge control. Heat pump compressor suction drums are provided because the column overhead is very high and the distance between the column overhead and the compressor suction is very long, which can lead to long residence times and the possibility of greater ambient heat loss. Separate multistage heat recovery compressors are used to recover heat from the deethanizer overhead and the PP splitter overhead and transfer it to the deprotonator for reboiling. Heat recovery compressors are also centrifugal compressors with surge protection control. The heat pump compressor and the heat recovery compressor are preferably separate machines because the steam flow rate of the heat pump compressor is more than 10 times the volume flow of the heat recovery compressor. In addition, having separate machines allows for flexibility in adjusting the duty of the deethanizer overhead condenser without changing the duty of the PP splitter reboiler, thereby keeping the columns independent.

In the process and system of the present invention, the PP splitter overhead pressure is controlled by adjusting the heat recovery compressor flow rate. Higher flow rates through the heat recovery compressor will allow more duty to be extracted by the depropanizer top reboiler and propylene trim cooler. This provides better control of the column overhead pressure. Additionally, deethanizer off-gas exchangers are used to supercool the deethanizer stripper reflux to reduce the vapor load at the deethanizer rectifier and to reduce the rectifier condenser duty and the stripper condenser duty. Finally, the temperature of the deethanizer rectifier condenser is controlled by adjusting the heat recovery first stage suction drum pressure. In addition, heat removed from the deethanizer overhead can be used to reboile the depropanizer. In previous designs, this heat was dissipated with air or cooling water.

Thus, in one aspect, the present invention provides a method for preparing a gas stream comprising the steps of: separating a stream comprising C4- hydrocarbons into an overhead stream and a C3 + bottom stream in a first separation zone; Separating the C3 + bottoms stream into a bottoms stream comprising propylene overheads stream and propane in a second separation zone; Compressing the propylene overhead stream in a first compression zone configured to provide a compressed propylene overhead stream; Recovering heat from the first portion of the compressed propylene overhead stream in a heat exchange zone associated with a second separation zone; Condensing a second portion of the compressed propylene overhead stream in the separation vessel, the separation vessel providing a propylene vapor stream and a propylene liquid stream; Reducing the pressure of at least a portion of the propylene liquid stream to provide a reduced pressure stream; Recovering heat by reduced pressure steam in a second heat exchange zone, the second heat exchange zone being associated with the first separation zone and configured to condense a portion of the overhead stream and provide a vaporized propylene stream. ; Compressing the vaporized propylene stream in a second compression zone configured to provide a recompressed propylene stream; And mixing the recompressed propylene stream with a second portion of the compressed propylene overhead stream in a separation vessel.

Thus, in another aspect, the present invention provides a method of separating a stream comprising: separating a stream in a first separation zone configured to separate the stream into an overhead stream and a C3 + substream; Separating the C3 + bottoms stream and delivering the C3 + bottoms stream to a second separation zone configured to provide a propylene overhead stream and a bottoms stream, the bottoms stream comprising propane; Passing the bottoms stream of the second separation zone to the third separation zone; Delivering the propylene overhead stream to a first compression zone configured to compress the propylene overhead stream to provide a compressed propylene overhead stream; Delivering a first portion of the compressed propylene overhead stream to a heat exchange zone associated with a second separation zone, configured to remove heat from the first portion of the compressed propylene overhead stream; Delivering a second portion of the compressed propylene overhead stream to a separation vessel configured to allow the second portion of the compressed propylene overhead stream to cool and separate into a vapor propylene stream and a liquid propylene stream; Reducing the pressure of at least a portion of the liquid propylene stream to provide a reduced pressure stream, wherein the reduced pressure stream comprises a mixture of liquid and vapor; Delivering a reduced pressure stream to a second heat exchange zone associated with the first separation zone and configured to vaporize liquid in the reduced pressure stream and provide a vaporized propylene stream, wherein the second heat exchange zone is also overhead from the first separation zone. Acquiring a portion of a stream; Delivering the vaporized propylene stream to a second compression zone configured to compress the vaporized propylene stream to provide a recompressed propylene stream; And delivering a recompressed propylene stream to a separation vessel.

In another aspect, the present invention provides an apparatus for manufacturing a fuel cell comprising: a first separation zone comprising a fractionation column configured to obtain a stream and separate it into an overhead stream and a C3 + bottoms stream; A second separation zone comprising a fractionation column configured to obtain and separate a C3 + bottoms stream to provide a propylene overhead stream and a bottoms stream, the bottoms stream comprising propane; A first compression zone configured to compress the propylene overhead stream to provide a compressed propylene overhead stream; A heat exchange zone associated with the second separation zone and configured to remove heat from the first portion of the compressed propylene overhead stream; A separation vessel configured to obtain a second portion of the compressed propylene overhead stream into a vapor propylene stream and a liquid propylene stream; A valve configured to obtain a portion of the liquid propylene stream and provide a reduced pressure stream; A second heat exchange zone associated with the first separation zone and configured to heat the reduced pressure portion to provide a vaporized propylene stream; A second compression zone configured to compress the reduced pressure stream and the vapor propylene stream to provide a recompressed propylene stream; And one or more lines configured to deliver the recompressed propylene stream to the separation vessel.

Further aspects, objects, embodiments, and details of the invention are described in the following detailed description of the invention.

In the drawing,
1 illustrates a system and process flow diagram in accordance with one or more embodiments of the present invention.
2 illustrates a portion of a process flow diagram in accordance with one or more embodiments of the present invention.
Justice
As shown, the process flow lines in the figures are interchangeable, for example lines, pipes, branches, distributors, streams, effluents, feeds, products, parts, catalysts, withdrawal, May be referred to as recycling, aspiration, release, and caustic.
As used herein, the term “zone” may refer to an area that includes one or more equipment items and / or one or more subzones. The equipment item may comprise one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers. In addition, equipment items such as reactors, dryers, or vessels may further comprise one or more zones or subzones.
As used herein, the term "vapor" may refer to a gas or dispersion that may comprise or consist of one or more hydrocarbons.
As used herein, the term "stream" may include various hydrocarbon molecules and other materials. Furthermore, the term "stream comprising Cx hydrocarbons" or "stream comprising Cx olefins" refers to a stream comprising hydrocarbon or olefin molecules each having "x" carbon atoms, suitably "x" carbon atoms each. Streams with the majority of hydrocarbons or olefins having, and preferably at least 75% by weight, of hydrocarbon molecules each having " x " carbon atoms. Moreover, the term "stream comprising Cx + hydrocarbons" or "stream comprising Cx + olefins" comprises mostly hydrocarbon or olefin molecules each having "x" or more carbon atoms, suitably each (x-1) It may comprise a stream comprising less than 10% by weight and preferably less than 1% by weight of hydrocarbon or olefin molecules having carbon atoms. Finally, the term "Cx-stream comprises mostly hydrocarbon or olefin molecules each having up to" x "carbon atoms, suitably 10 weights of hydrocarbon or olefin molecules each having (x + 1) carbon atoms. It may comprise a stream comprising less than% and preferably less than 1% by weight.
As used herein, the term "overhead stream" may refer to a stream exiting at or near the top of a vessel, such as a column.
The term "column" means a distillation column or columns for separating one or more components of different volatilities. Unless otherwise indicated, each column includes a condenser on the overhead of the column to condense the overhead vapor and return a portion of the overhead stream back to the top of the column. A reboiler is also included at the bottom of the column to vaporize a portion of the bottom stream and send it back to the bottom of the column to provide fractional energy. The feed to the column can be preheated. The upper pressure is the pressure of the overhead vapor at the outlet of the column. The bottom temperature is the liquid bottom outlet temperature. Overhead and bottom lines refer to the net line from the column at reflux or downstream of the reboiler to the column.
As used herein, the term "bottom stream" may refer to a stream exiting at or near the bottom of a vessel, such as a column.

Methods have been developed that allow more efficient separation of various hydrocarbons by increasing heat recovery therefrom. In certain applications of the present invention, innovations are used in conjunction with deethanizers and PP splitters. The deethanizer requires a cold condensation system to recover the C3 material and to reject the C2-material as steam. This separation is performed at high pressure (400 psig) at 2,758 μg to keep the material in the liquid phase in the overhead receiver. The deethanizer cooling system is typically a skid mounted system consisting of a two-stage compressor, two disengaging drums, an accumulator, and a chiller (air or water cooled exchanger). Typically, this is an additional unit that must be purchased, which can increase the overall capital expenditure and complexity of the system, which increases the number of plant equipment. Additionally, these cooling units can typically use oil flooded screw compressors for some catalytic dehydrogenation units that handle less than 500 kmta (1,000 metric tons per year). Such screw compressors are typically not as reliable as centrifugal compressors.

Thus, the process and system of the present invention condenses the deethanizer rectifier overhead using a PP splitter overhead system instead of using a separate modular skid cooling unit. Cooling units usually use propylene as the refrigerant available at the PP splitter overhead. In this integrated manner, two compressors: a heat pump compressor used to reboile the PP splitter and to condense the primary reflux material for the PP splitter; And heat recovery compressors that condense the PP splitter secondary reflux and net overhead material and also condense the deethanizer rectifier overhead material. It is desirable to have these compressors as separate machines because the steam flow rate to the heat pump compressor is much higher than the steam flow rate to the heat recovery compressor. In addition, the use of separate compressors provides better control when it is necessary to adjust the deethanizer's duty without affecting the PP splitter.

Heat from condensation of these two columns can be recovered and transferred to the depropanizer as reboiling heat. Extraction of heat from the deethanizer rectifier overhead allows more heat to be transferred to the depropanizer heat recovery reboiler, reducing the LP steam consumption of the depropanizer. This is believed to cause a significant reduction in utility as well as a reduction in capital costs. These and other effects will be understood in light of the following description of some of the embodiments of the invention.

Referring to FIG. 1, the present invention will be described with reference to a system, generally designated 10. As shown, a feed stream 12 containing hydrocarbons to be separated is passed to the first separation zone 14. Feed stream 12 may comprise, for example, a liquid effluent from the cryogenic separation unit and comprises C4- hydrocarbons.

In a preferred embodiment, the first separation zone 14 comprises at least one fractionation column 16 for separating hydrocarbons in the feed steam 12 based on the boiling point. In the most preferred embodiment, the fractionation column 16 in the first separation zone 14 comprises a deethanizer stripping column (or deethanizer stripper). The purpose of section 14 is to remove C2- hydrocarbons and lighter materials from C3 + hydrocarbons.

As is known, fractionation column 16, for example a deethanizer stripping column, is operated under conditions that separate hydrocarbons in feed stream 12 into overhead vapor stream 18 and bottom stream 20. In at least one embodiment, fractionation column 16 is operated at an overhead pressure of 2,930 psig (425 psig). From the deethanizer stripping column, the bottom stream 20 will comprise C3 + hydrocarbons, and the overhead vapor stream 18 will primarily comprise C2- hydrocarbons, but probably some C3 + hydrocarbons.

Thus, in order to recover some of the heavier hydrocarbons from the overhead vapor stream 18, the overhead vapor stream 18 is cooled, for example in a heat exchanger 22, with chilled water (or air cooled) and partially condensed. Overhead stream 24 may be provided. The partially condensed stream 24 is passed to another fractionation column 26, for example a deethanizer rectifier, in the first separation zone 14, where the components of the partially condensed stream 24 are transferred to the second fractionation stream. At the bottom of the fractionation column 26 can be separated into liquid and vapor phases. The vapor will be further fractionated in the second fractionation column 26, where the C2-material will be removed from the C3 material. The overhead liquid stream 28 from the second fractionation column 26 can be passed back to the first fractionation column 16 as reflux to the stripping column. Vapor stream 30 from second fractionation column 26 is condensed in heat exchange zone 32 where liquid stream 34a (containing C3 hydrocarbons) can be refluxed back to second fractionation column 26. On the other hand, off-gas stream 34b comprising C2- and lighter components can be further processed.

2- for the first separation zone 14, with an air cooler or water cooler in the middle (in the heat exchanger 22) to reduce the cooling duty required for the heat exchange zone 32 for the vapor stream 30. Preference is given to using column systems. However, designs are also contemplated that have a single column integrating both fractionation columns 26, 16 without intermediate cooling in heat exchanger 22. In a single column system for the first separation zone 14 without intermediate cooling, the cooling duty of the heat exchange zone 32 required will be greater. Since cooling duty is typically more expensive than air or water cooling, it may be economically desirable to use a two-column system for the first separation zone 14 as shown.

As discussed above, the heat exchange zone 32 typically utilizes a cold condensation system for the second fractionation column 26 and vapor stream 30 from the vapor / liquid separation drum. In the process and system of the present invention, condensation of the vapor stream 30 from the second fractionation column 26 is achieved by a separate cooling unit using propylene or lighter material as the heat exchange medium.

More specifically, back to the fractionation column 16, the bottom stream 20 from the first separation zone 14 is passed to the second separation zone 36. The second separation zone 36 comprises at least one fractionation column 38 for separating hydrocarbons in the bottom stream 20 from the fractionation column 16 in the first separation zone 14 based on the relative volatility. do. In the most preferred embodiment, the fractionation column 38 in the second separation zone 36 comprises a propylene-propane splitter column that produces polymer grade propylene in the net overhead and propane in the net bottom.

As is known, the fractionation column 38, such as the propylene-propane splitter column, of the second separation zone 36 may contain hydrocarbons in the bottom stream 20 from the fractionation column 16 in the first separation zone 14. It operates under conditions that separate into another overhead vapor stream 40 and another bottom stream 42. In at least one embodiment, fractionation column 38 is operated at an overhead pressure of 689 kg (100 psig). From the propylene-propane splitter column, the bottom stream 42 will comprise at least 90% by weight propane and heavier hydrocarbons, and the overhead vapor stream 40 will comprise a propylene overhead stream. The bottom stream 42 from the second separation zone 36 is to be passed to another separation zone 100 (see FIG. 2), which may include a depropanizer column 102, discussed in more detail below. Can be.

The remainder of the description will relate to the embodiment where the fractionation column 38 in the second separation zone 36 comprises a PP splitter; It is not intended to be limiting.

The overhead vapor stream 40 or propylene overhead stream from the fractionation column 38 in the second separation zone 36 is transferred to the liquid knockout drum 44 and then to the first compression zone 46. do. The first compression zone 46 includes a single stage heat pump compressor 48, which produces a product comprising primarily propylene and comprises a compressed propylene stream 50. The heat pump compressor 48 compresses the overhead vapor stream 40 from the fractionation column 38 in the second separation zone 36 to a maximum of 207 psig (175 psig) to form a compressed propylene stream 50. will be.

Compressed propylene stream 50 is divided into at least two portions 50a, 50b, wherein 75 to 90% (eg, first portion 50a) is heat (or heat pump) from compressed propylene stream 50 ) Is transferred to the heat exchange zone 52 for recovery and delivery. More specifically, heat is transferred from the high temperature side of the heat exchanger 54 in the heat exchange zone 52 to the low temperature side to serve as a heat source for reboiling the fractionation column 38 in the second separation zone 36. do. The heat exchanger 54 as well as the other heat exchangers discussed herein may also be of any conventional design, one example of which is a cross-flow (TEMA X shell) shell-in-tube In-tube design, another example uses high heat transfer techniques such as Highflux ™ (available from UOP, Des Plaines, Ill.) or plate type exchanger. The vapor at the hot side outlet of the heat exchanger 54 is fully condensed and passed back to the fractionation column 38 in the second separation zone 36 as the primary reflux material. In order to control the flow of the first portion 50a of the compressed propylene stream 50 back to the fractionation column 38 in the second first separation zone 36, the outlet of the heat exchanger 54 is the valve 55. It can include a pressure drop of 5 to 25 psi (34 to 172 kPa) through.

The second portion 50b (preferably the remaining 10-25%) of the compressed propylene stream 50 bypasses the heat exchange zone 52 and preferably has an operating pressure of 1,241 kg (175 psig). Is delivered to a separation vessel 56 containing a second stage suction drum. In separation vessel 56, compressed propylene stream 50 is cooled, for example by contact with another stream (discussed below), to condense a portion of the vapor in separation vessel 56. Thus, separation vessel 56 will provide vapor propylene stream 58 and liquid propylene stream 60.

A portion 60a of the liquid propylene stream 60 may be recovered (as net overhead product). In addition, the other portion 60b of the liquid propylene stream 60 passes through the line as a secondary reflux due to the pressure difference between the separation vessel 56 and the overhead pressure of the fractionation column 38 in the second separation zone 36. It may be passed back to the fractionation column 38 in the second separation zone 36. The valve 57 may reduce the pressure of the second portion 60b of the liquid propylene stream 60. The third portion 60c of the liquid propylene stream 60 is flashed to a lower pressure (20-50 psig), for example via valve 61, to provide a reduced pressure stream 63 This may then be used to recover heat from the first separation zone 14. This will replace the cooling unit discussed above.

Returning to FIG. 1, in the illustrated process, the reduced pressure stream 63 is delivered from the valve 61 to the heat exchanger 62 and associated with the vapor stream 30 of the first separation zone 14 discussed above. . The reduced pressure stream 63 will typically contain a mixture of liquid and vapor. In the heat exchanger 62, the liquid portion of the reduced pressure portion 63 will preferably be vaporized at the shell side of the kettle (TEMA K shell) heat exchanger. The vaporized propylene stream 64 can be transferred from the heat exchanger 62 to the stage suction drum 66 discussed below. Additionally, as discussed above, in the heat exchange zone 32 with the heat exchanger 62, a portion of the vapor stream 30 is condensed and a second in the first separation zone 14 in the stream 34a. It will be passed back to the fractionation column 26.

The vaporized propylene stream 64 is to a second stage suction drum 66 (at a pressure of 20 to 50 psig) (138 to 345 kgg) and then to a second compression zone 68 having a heat recovery compressor 70. Is passed to. The heat recovery compressor 70 may also process a portion of the vapor propylene stream 58 from the separation vessel 56. In the heat recovery compressor 70, the vapor streams 58, 64 will be compressed to 2,689 kg (390 psi). From the heat recovery compressor 70, the recompressed propylene stream 72 can be returned to the separation vessel 56. However, since the recompressed propylene stream 72 contains recoverable heat, it is preferred that heat from the recompressed propylene stream 72 be recovered first.

For example, heat from the recompressed propylene stream 72 can be recovered or removed in the heat exchange zone 74. Preferably, referring to FIG. 2, heat exchange zone 74 is associated with the reboiler of depropanizer column 102. The depropanizer column 102 is typically used to separate the bottom stream 42 from the fractionation column 36 in the second separation zone 36.

Exemplary depropanizer column 102 generates column overhead stream 104 containing C4 + components and net overhead stream 120 comprising C3-material. Reboiler return stream 106 is vaporized in steam reboiler 108 and then returned to deprotonizer column 102.

Overhead stream 110 from depropanizer column 102 is cooled in heat exchanger 112 and sent to column overhead receiver 114. Condensed stream 116 is separated into reflux stream 118, which is sent to depropanizer column 102, and recoverable propane stream 120.

The heat exchange zone 74 used to recover heat from the recompressed propylene stream 72 preferably includes a reboiler 122, which is supplied from the liquid accumulator tray 124. The recompressed propylene stream 72 is used to heat the recycle stream 126 in the reboiler 122 to provide heat to the depropanizer column 102. This is merely an example configuration.

Returning to FIG. 1, the heat exchange zone associated with another heat exchange zone 76, for example a PP splitter trim cooler, before the recompressed propylene stream 72 is delivered to the separation vessel 56 as discussed above. This recompression propylene stream 72 can be used to supercool. Heat exchanger 76 is used to remove residual heat from the process and is typically an air or water cooled exchanger. In the vapor / liquid separation vessel 56, the recompression C3 overhead stream 72 will be separated as discussed above.

Processes and systems in accordance with one or more embodiments described herein are believed to provide more efficient heat recovery, as well as the capital savings required to implement such processes and systems.

Various other components, such as valves, pumps, filters, coolers, etc., are not shown in the drawings because their details are well within the knowledge of those skilled in the art and their description is not necessarily required to practice or understand embodiments of the present invention. It should be recognized and understood by those skilled in the art.

Specific embodiment

While the following is described in connection with specific embodiments, it will be understood that this description is intended to be illustrative, and not to limit the scope of the foregoing description and the appended claims.

A first embodiment of the invention comprises the steps of: separating a stream comprising C4- hydrocarbons into an overhead stream and a C3 + bottoms stream in a first separation zone; Separating the C3 + bottoms stream into a bottoms stream comprising propylene overheads stream and propane in a second separation zone; Compressing the propylene overhead stream in a first compression zone configured to provide a compressed propylene overhead stream; Recovering heat from the first portion of the compressed propylene overhead stream in a heat exchange zone associated with a second separation zone; Condensing a second portion of the compressed propylene overhead stream in the separation vessel, the separation vessel providing a propylene vapor stream and a propylene liquid stream; Reducing the pressure of at least a portion of the propylene liquid stream to provide a reduced pressure stream; Recovering heat by reduced pressure steam in a second heat exchange zone, the second heat exchange zone being associated with the first separation zone and configured to condense a portion of the overhead stream and provide a vaporized propylene stream. ; Compressing the vaporized propylene stream in a second compression zone configured to provide a recompressed propylene stream; And mixing the recompressed propylene stream with a second portion of the compressed propylene overhead stream in a separation vessel. One embodiment of the present invention further includes the step of compressing the propylene vapor stream from the separation vessel in the second compression zone, the implementation of one of the previous embodiments of this paragraph up to the first embodiment of this paragraph. Form, arbitrary embodiment, or all embodiments. One embodiment of the present invention further includes removing heat from the recompressed propylene stream before the recompressed propylene stream is mixed with the second portion of the compressed propylene overhead stream in the separation vessel. One embodiment, any embodiment, or all of the previous embodiments of this paragraph up to the embodiment. One embodiment of the present invention wherein the heat is removed from the recompressed propylene stream in a third heat exchange zone associated with a third separation zone configured to receive a bottoms stream from the second separation zone 36. It is one embodiment, any embodiment, or all of the previous embodiments of this paragraph up to the embodiment. One embodiment of the present invention further comprises separating the first portion of the compressed propylene overhead stream in the fractionation column in the second separation zone, prior to this paragraph up to the first embodiment of this paragraph. One of these, any, or all of the embodiments. One embodiment of the present invention further comprises recovering a second portion of the propylene liquid stream as a propylene product stream, wherein one of the previous embodiments of this paragraph up to the first embodiment of this paragraph. , Any embodiment, or all embodiments. One embodiment of the present invention further includes the step of refluxing the third portion of the propylene liquid stream from the separation vessel to the fractionation column in the second separation zone, up to the first embodiment of this paragraph. One of the embodiments, any embodiment, or all embodiments. In one embodiment of the present invention, previous embodiments of this paragraph up to the first embodiment of this paragraph wherein the first separation zone comprises two fractionation columns and the second separation zone comprises one fractionation column. Either one embodiment, any embodiment, or all embodiments. One embodiment of the present invention further includes transferring heat from the recompressed propylene stream to the third separation zone configured to receive the bottoms stream from the second separation zone. One of the previous embodiments of the paragraph, any embodiment, or all embodiments.

A second embodiment of the present invention comprises the steps of: separating a stream in a first separation zone configured to separate the stream into an overhead stream and a C3 + substream; Separating the C3 + bottoms stream and delivering the C3 + bottoms stream to a second separation zone configured to provide a propylene overhead stream and a bottoms stream, the bottoms stream comprising propane; Passing the bottoms stream of the second separation zone to the third separation zone; Delivering the propylene overhead stream to a first compression zone configured to compress the propylene overhead stream to provide a compressed propylene overhead stream; Delivering a first portion of the compressed propylene overhead stream to a heat exchange zone associated with a second separation zone, configured to remove heat from the first portion of the compressed propylene overhead stream; Delivering a second portion of the compressed propylene overhead stream to a separation vessel configured to allow the second portion of the compressed propylene overhead stream to cool and separate into a vapor propylene stream and a liquid propylene stream; Reducing the pressure of at least a portion of the liquid propylene stream to provide a reduced pressure stream, wherein the reduced pressure stream comprises a mixture of liquid and vapor; Delivering a reduced pressure stream to a second heat exchange zone associated with the first separation zone and configured to vaporize liquid in the reduced pressure stream and provide a vaporized propylene stream, wherein the second heat exchange zone is also overhead from the first separation zone. Acquiring a portion of a stream; Delivering the vaporized propylene stream to a second compression zone configured to compress the vaporized propylene stream to provide a recompressed propylene stream; And delivering the recompressed propylene stream to a separation vessel. One embodiment of the present invention further includes the step of delivering a vapor propylene stream from the separation vessel to the second compression zone, the implementation of one of the previous embodiments of this paragraph up to the second embodiment of this paragraph. Form, arbitrary embodiment, or all embodiments. One embodiment of the present invention further includes one of the previous embodiments of this paragraph up to the second embodiment of this paragraph further comprising removing heat from the recompressed propylene stream before the propylene is delivered to the separation vessel. Is any embodiment, any embodiment, or all embodiments. One embodiment of the invention provides a method of delivering a recompressed propylene stream to a third heat exchange zone associated with a third separation zone, and then delivering the recompressed propylene stream from the third heat exchange zone to a separation vessel. Is one embodiment, any embodiment, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph, further including. One embodiment of the present invention further includes passing the first portion of the compressed propylene overhead stream from the first heat exchange zone to the fractionation column in the second separation zone, up to the second embodiment of this paragraph. One of the previous embodiments of this paragraph, any embodiment, or all embodiments. One embodiment of the present invention further comprises recovering a second portion of the liquid propylene stream as a propylene product stream, one of the previous embodiments of this paragraph up to the second embodiment of this paragraph. , Any embodiment, or all embodiments. One embodiment of the invention further includes passing the third portion of the liquid propylene stream to the fractionation column in the second separation zone, up to the second embodiment of this paragraph. One embodiment, any embodiment, or all embodiments. In one embodiment of the present invention, prior embodiments of this paragraph up to the second embodiment of this paragraph wherein the first separation zone comprises one fractionation column and the second separation zone comprises one fractionation column Either one embodiment, any embodiment, or all embodiments. One embodiment of the present invention further includes one of the previous embodiments of this paragraph up to the second embodiment of this paragraph further comprising removing heat from the recompressed propylene stream before the propylene is delivered to the separation vessel. Is any embodiment, any embodiment, or all embodiments.

A third embodiment of the present invention includes a first separation zone comprising a fractionation column configured to obtain a stream and separate it into an overhead stream and a C3 + bottoms stream; A second separation zone comprising a fractionation column configured to obtain and separate a C3 + bottoms stream to provide a propylene overhead stream and a bottoms stream, the bottoms stream comprising propane; A first compression zone configured to compress the propylene overhead stream to provide a compressed propylene overhead stream; A heat exchange zone associated with the second separation zone and configured to remove heat from the first portion of the compressed propylene overhead stream; A separation vessel configured to obtain a second portion of the compressed propylene overhead stream into a vapor propylene stream and a liquid propylene stream; A valve configured to obtain a portion of the liquid propylene stream and provide a reduced pressure stream; A second heat exchange zone associated with the first separation zone and configured to heat the reduced pressure portion to provide a vaporized propylene stream; A second compression zone configured to compress the reduced pressure stream and the vapor propylene stream to provide a recompressed propylene stream; And one or more lines configured to deliver the recompressed propylene stream to the separation vessel. One embodiment of the present invention further includes a third heat exchange zone configured to remove heat from the recompressed propylene stream, wherein the third heat exchange zone is disposed between the separation vessel and the second compression zone. One embodiment, any embodiment, or all of the previous embodiments of this paragraph up to the third embodiment.

Without further elaboration, using the foregoing description, various changes and modifications of the present invention can be made by those skilled in the art without departing from the spirit and scope of the present invention, making the best use of the present invention and easily identifying essential features of the present invention. It is believed that this can be achieved and adapted to various uses and conditions. Accordingly, the foregoing preferred specific embodiments are to be construed as illustrative only, without restricting the remainder of the invention in any way, and are intended to cover various modifications and equivalent arrangements falling within the scope of the appended claims.

In the above, unless otherwise indicated, all temperatures are described in degrees Celsius, and all parts and percentages are by weight.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be understood that a vast number of variations exist. It is also to be understood that the example embodiments or example embodiments are merely examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, but that is outside the scope of the invention as set forth in the appended claims and their legal equivalents. It is understood that various changes may be made in the function and arrangement of elements described in the example embodiments without this.

Claims (10)

As a method of separating hydrocarbons and recovering heat,
Separating the stream comprising C4- hydrocarbons into an overhead stream and a C3 + bottoms stream in a first separation zone;
Separating the C3 + bottoms stream into a bottoms stream comprising a propylene overhead stream and propane in a second separation zone;
Compressing the propylene overhead stream in a first compression zone configured to provide a compressed propylene overhead stream;
Recovering heat from the first portion of the compressed propylene overhead stream in a heat exchange zone associated with the second separation zone;
Condensing a second portion of the compressed propylene overhead stream in a separation vessel, the separation vessel providing a propylene vapor stream and a propylene liquid stream;
Reducing the pressure of at least a portion of the propylene liquid stream to provide a reduced pressure stream;
Recovering heat by the reduced pressure steam in a second heat exchange zone, wherein the second heat exchange zone is associated with the first separation zone and is configured to condense a portion of the overhead stream and provide a vaporized propylene stream. Wherein, the step;
Compressing the vaporized propylene stream in a second compression zone configured to provide a recompressed propylene stream; And
Mixing the recompressed propylene stream with the second portion of the compressed propylene overhead stream in the separation vessel.
Including, the method. The method of claim 1, further comprising compressing the propylene vapor stream from the separation vessel in the second compression zone. The method of claim 1, further comprising removing heat from the recompressed propylene stream before the recompressed propylene stream is mixed with the second portion of the compressed propylene overhead stream in the separation vessel. The method of claim 1, wherein the heat is removed from the recompressed propylene stream in a third heat exchange zone associated with a third separation zone configured to withdraw the bottom stream from the second separation zone. 5. The process of claim 1, further comprising separating the first portion of the compressed propylene overhead stream in a fractionation column in the second separation zone. 6. The process according to claim 1, further comprising recovering the second portion of the propylene liquid stream as a propylene product stream. 5. The method of claim 1, further comprising refluxing the third portion of the propylene liquid stream from the separation vessel to a fractionation column in the second separation zone. 6. 5. The method of claim 1, wherein the first separation zone comprises two fractionation columns and the second separation zone comprises one fractionation column. 6. 5. The method of claim 1, wherein the first separation zone comprises one fractionation column and the second separation zone comprises one fractionation column. 6. A system for separating hydrocarbons and recovering heat,
A first separation zone comprising a fractionation column configured to obtain a stream and separate it into an overhead stream and a C3 + bottoms stream;
A second separation zone comprising a fractionation column configured to obtain and separate the C3 + bottoms stream to provide a propylene overhead stream and a bottoms stream, the bottoms stream comprising propane;
A first compression zone configured to compress the propylene overhead stream to provide a compressed propylene overhead stream;
A heat exchange zone associated with the second separation zone and configured to remove heat from the first portion of the compressed propylene overhead stream;
A separation vessel configured to obtain a second portion of the compressed propylene overhead stream and separate it into a vapor propylene stream and a liquid propylene stream;
A valve configured to receive a portion of the liquid propylene stream and provide a reduced pressure stream;
A second heat exchange zone associated with said first separation zone and configured to heat said reduced pressure stream to provide a vaporized propylene stream;
A second compression zone configured to compress the vaporized propylene stream and the vapor propylene stream to provide a recompressed propylene stream; And
One or more lines configured to deliver the recompressed propylene stream to the separation vessel
Including, the system.

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